Condition responsive instrument



Oct. 26, 1943. c, v BULLEN I 2,332,985

' CONDITION RESPONSIVE INSTRUMENT Filed Sept. 8, 1941 ENVENTOR CYZdr/I V b'ullefi f, 1 WWI I ATTORNEYS Patented Oct. 26, 1943 jum'rsn STATES PAiE NT OFFICE CONDITION RESPONSIVE Ingram-NT Clark v. Bullen, Rockford, 111., sisipiiir to Barber-Coleman Company, Rockford, 111., a corporation of Illinois 5 Claims.

This invention relates to condition responsive instruments in which the eflective control point may be varied progressively by changing the energization of an electromagnet exerting a force which counteracts the stress produced by the condition ponsive element of the instrument.

The gener object is to provide an instrument of the above character which is simple in construction and is reliable in operation when subjected to severe vibration.

The invention also resides in the novel manner of applying the electromagnetic force.

Other objects and advantages of the invention will become apparent from the following detailed description taken in connection with the accompanyins drawing, in which Figur 1 is a front elevational view of a condition responsive instrument embodying the novel features of the present invention, the front of the instrument casing and certain of the parts being shown in section.

Fig. 2 is a side elevational view with the casin shown in section.

as switch actuating arms 5 and 6 movable independently of each other in response to the same condition changes and each acted on directly by a single electromagnet 1 which counteracts the condition responsive forces acting on both arms.

Each element is moved with a detent or snap action so that it always occupies one of two definite positions, there being four positions for the two elements. Control devices comprising two pairs of switches 8 and 9 and i and ii are actuated by the respective elements and 6 and these devices may be utilized to control a r v rsible power operator.

While the movement of the control arm 5 and i may be effected by a single condition responsive means. individual means are employed in the present embodiment and arranged to respond to ambient temperature changes. Accordingly, the arms 5 and 6 are carried by thermostatic members in the form of separate strips 12 and i3 of bimetal which, as shown, are bent to form loops adjustably mounted on one end on an insulating base H. the other or free endshaving the associated control arms secured thereto as by rivets l5 and supported in vertical position.

Herein, the strip i2 is coiled with Invar or metal of low expansibility on the outside while the metal layer of higher expansibility is on the inside. As a result, the arm I is urged toward the right in response to a fall in the temperature influencing the member II. The metal layers of the strip i3 are reversed, the Invar being on the inside so that the arm 8 is urged to th left in response to a fall in the ambient temperature and to the'right as the temperature rises.

Near its upper end, the arm I is disposed between stationary contacts i8 and I! mounted on the base It and coacting with the arm to form the control switches 8 and 8. Similarly, the arm 6 coacts with stationary contacts i8 and i9 to form the switches iii and il. Thus, the thermostatic strip l2 and I3 and the associated arms and switches in eflect constitute separate thermostats 20 and ii.

The thermostat member I! is fixed at 22 to a lever 23 which is fulcrumed on the pin 24 on the base it. At its upper end, the lever 23 is Joined by a connection 25 to a lever 28 pivoted at 2l, the connection being below the pivot so that by shifting the lower end of the lever 26, the control point of the thermostat 20 may be raised or lowered as desired. The thermostatic strip i3 is similarly mounted except that the connection 25 between the levers 23' and 25 is disposed above the pivot 21' so that the normally fixed end of the strip I: will be adjusted in a direction opposite to that of the strip i! when the two levers 28 and 26' are moved in the same direction. The levers are connected at their lower ends by a flexible bar 28 and one lever has a downwardly projecting handle 29 by which the two levers may be shifted together and the effective control points oi the two thermostats adjusted in unison.

Means is provided for causing the arms 5 and 8 to move between their contacts with a quick snap action, thereby avoiding arcing at the contact surfaces when the instrument is subjected to severe vibration. This means may comprise magnetic detents 30 and 3| having permanent magnetic pole faces 32-33 and 32'33' spaced slightly farther apart than the surfaces of the stationary switch contacts and disposed on opposite sides of the switch arms which are composed of magnetic material such as soft iron. The arrangement is such that when either arm is disposed midway between its contacts; it will be centered magnetically with respect to the magnetic pole faces. Thus, the arm 5 moves against the contact 11 to close the switch 8 whenever the ambient temperature rises above a value predetermined by the setting of the lever 26. Simi- 2 larly, when the temperature falls below a slightly lower value, the stress in the bimetal is changed sumciently to overcome the detent action and cause reverse movement of the arm and closure of the switch 8. The temperature range below and above which the switches 8 and 9 are respectively closed may be made comparatively narrow, usually about one degree Fahrenheit. The thermostat 2| operates in the same way except that the arm 6 is moved to the left to close the switch III in response to a fall in temperature. Preferably, it is adjusted so that its control range is slightly lower, about one degree, than that of the thermostat 20.

The electromagnet 1 by which the control points or the two thermostats are shifted simultaneously with changes in the energization of the magnet comprises a coil 33" wound around a core 34 which is supported at opposite ends by brackets 35 secured to the base i4. The magnet is mounted between the extended upper ends of the arms and 6 with its axis disposed horizontally. The ends of the control arms are thus disposed adiacent the magnet poles 38 and 31 and constitute armatures which are attracted toward each other by the magnet, the movements of these armatures being limited by the stationary switch contacts so that the armatures are spaced from the magnet polesbut nevertheless are disposed within the magnetic influence of the latter.

It will be observed from the foregoing that as the energization of the magnet winding 33* is increased, the magnetic force exerted on the arms 5 and 8 will be correspondingly increased and, although the attracting forces act on the arms in opposite directions, the control points of the two thermostats will, due to the reversed arrangement of the bimetal layers, both be raised. Similarly, as the magnet energization is decreased, the oppositely acting attracting forces will be decreased and the control points oi. the twothermostats correspondingly lower. The use of a simple magnet construction and mounting of the two thermostats side by side on the base is made possible simply by reversing the bimetallic members l2 and I3 as described above.

Fig. 3 illustrates one way of utilizing the improved instrument in a temperature regulating system. In this case, the position of the damper 38 is modulated by a reversible electric motor 39 operating through gearing 40 to turn a shaft 4| connected to the damper. The motor wind lugs 42 and 43 have a common terminal connected through rotor 39 to one side of a current source 44. The other terminal of the winding 42 is connectedthrough a conductor 42 including a cam actuated limit switch 44 to the stationary switch contact I1. In a similar way, the winding 43 is connected through a conductor 45 and a limit switch 46 to the stationary contact I8. The

switch arms 5 and 8 are connected by a conductor 41 and the stationary contacts I5 and I9 are connected together and through a conductor 43 are connected to the other terminal of the current source. One terminal or the magnet winding 3i! is connected to the current source by a conductor 49 while the other terminal leads through a conduct-or 50 to a wiper arm 5| fast on the shaft 4|. This Wiper arm engages a resistance 52 opposite terminals of which are connected by conductors to opposite terminals of the current source.

With the parts positioned as shown in Fig. 3, the thermostat instrument is calling for heat and the control motor has run the damper to the :iully closed position and the face damper to full heating position determined by the limit switch 46. As the ambient temperature increases, the control point of the thermostat 2| will first be exceeded whereupon the arm 6 will be moved with a snap action to close the switch H. No circult is complete, however, until the temperature has risen further above the control point or the thermostat 20 whereupon the stress in the bimetal l2 overcomes the forces of the magnet and detent 33 and moves the arm 8 across the switch gap and against the contact H. A circuit for the motor winding 42 is thus completed extending from the battery through the conductor 48, switch arm 6, conductor 41, arm 5, switch 8, conductor 42', limit switch 44, the winding 42, and the rotor 39-. In the ensuing operation of the motor, the shaft 4| is turned counterclockwise correspondingly moving the damper toward cooling position. During this movement, the slider 5| moves across the resistance 52 increasing the voltage applied to the magnet i and correspondingly raising the effective control point of both thermostats. This movement continues until the magnetic force overcomes the stress of the bimetal i2 and the force of the detent 32 whereuponthe switch-9 is opened stopping the motor. As a result of this operation of the motor, the damper is advanced to a position exactly corresponding to the prevailing increased temperature. If the temperature continues to rise, the switch 5 will again be closed and further movement of the damper will take place until the thermostat 20 is again satisfied and the control point of the thermostat 2| correspondingly increased.

Assume now that the temperature falls below the prevailing control point of the thermostat while the switches 8 and H are both closed. The switch II! will be closed with a snap action and since the switch 8 is already closed, a circuit for the motor winding 43 is completed through the switches 8 and I0 and the limit switch 46. The motor runs in a direction to turn the shaft 4| clockwise to move the damper in the heat increasing direction. This is accompanied by a decrease in the magnet pull which permits the bimetal I3 to open the switch As before, the change in damper position will be exactly proportional to the ambient temperature decrease.

It will be observed from the foregoing that starting oi? the motor in opposite directions is initiated in response to closure of the switches 9 and in respectively as the ambient temperature rises above or falls below the operating range of the combined instrument which is determined by the settings of the individual thermostats. The two switches thus constitute the main control devices, the other switches 8 and II being included in the two circuits to prevent any possible closure otone circuit by its main switch at a time when the main switch of the other circuit is closed.

I claim as my invention:

l. A condition responsive instrument for controlling the operation of a conditioning means comprising, in combination, two control devices adapted for the control of said conditioning means differentially, elements movable independently of each other to actuate the respective devices at different values of the controlling condition, condition responsive means exerting variable control forces on said elements, detent means associated with the respective elements t cause movement of each element between two limit positions with a snap action, magnetic armatures carried by the respective elements, and an electromagnet having poles disposed adjacent said armatures and acting thereon to exert continuous but variable forces on said elements eounteracting the control forces acting on said, elements.

2. A condition responsive instrument for controlling the operation of a conditioning means, comprising, in combination, two spaced arms, condition responsive means exerting variable control forces on said arms tending to move the respective arms in opposite directions in response to similar condition changes, detent means for effecting movement of each arm between two limit positions with a snap action, control devices actuated by the respective arms atdifferent values of the condition and adapted for the control of said conditioning means differentially, said arms having portions thereof constituting magnetic armatures, and an electromagnet acting directly on said armature portions and exerting continuous but variable forces counteracting said control forces.

3. A condition responsive instrument for controlling the operation of a conditioning means, comprising, in combination, two elongated elements mounted side by side, condition responsive means exerting variable control forces on said elements tending to move the respective elements in opposite directions in response to similar condition changes, detent means causing movement of the respective elements with a snap action, control devices actuated by the respective elements at different values of the condition and adapted for the control of said conditioning means diiferentially, said elements having portions thereof constituting magnetic armatures, and an electromagnet disposed between said elements and having oppositely facing poles positioned ad- Jacent the respective armatures and exerting continuous but variable forces counteracting said control forces.

4. A condition responsive instrument for controlling the operation of a conditioning means, comprising, in combination, two control devices adapted for the control of said conditioning means diiferentially, elements movable independently of each other between two limit positions to actuate the respective devices at difierent values of the controlling condition, condition responsive means exerting variable control forces on said elements, detent means associated with the respective elements to cause movement there of between their limit positions with a snap action, said elements having parts composed of magnetic material, and an electromagnet having poles disposed adjacent said parts and acting thereon to exert continuous but variable forces on said elements counteracting the control forces acting on said elements.

5. A condition responsive instrument comprising, in combination, two control elements, means responsive to condition changes of the same character and exerting variable control forces on said elements tending to move the respective elements in opposite directions in response to similar condition changes, control devices actuated by the respective elements, separate adjusting means associated with the respective condition responsive means to vary the condition value at which the respective control devices are actuated, and a common means for actuating both of said adjusting means in unison but in reverse directions whereby to change the effective control points of said devices in the same direction.

CLARK V. BUILEN'. 

